Republic XP-69

Apteryx

ACCESS: Confidential
Joined
Sep 28, 2007
Messages
152
Reaction score
20
Hi, all...

To remind my readers the backstory on the p-69, aka AP-18::

Republic Aircraft had a WWII fighter project to be powered by a single Wright Tornado engine mid-mounted, a la the Airacobra. It was a new project, and not a development of their P-47.

I've seen at least one 3-view of the above-named fighter project, in a compilation of "project" drawings put out by the AAHS called Scale-Master Fax File no. 7. I've attached a scan. My question: why do you think that a new design would feature a wing planform with a constant-span inboard section? There's no dihedral break; no constant width in the center to go with the constant span. You see what I'm saying here?

One could hypothesize that some overworked engineer just stuck that section in as an insert on the drawing to increase wing area to a specified amount, but one has a harder time believing the plane would have progressed to prototype status with that feature. But I may be missing something. Any thoughts?
 

Attachments

  • xp-69 3-view.jpg
    xp-69 3-view.jpg
    49 KB · Views: 1,169

Artie Bob

ACCESS: Confidential
Joined
Jan 6, 2008
Messages
175
Reaction score
52
AFAIK, the XP-69 did not reach prototype status, mockup only, with a configuration different from the drawing shown.

Best regards,

Artie Bob
 

Justo Miranda

ACCESS: Above Top Secret
Senior Member
Joined
Dec 2, 2007
Messages
5,351
Reaction score
4,723
Website
www.amazon.com
Mockup and early drawing here
 

Attachments

  • Escanear0001.jpg
    Escanear0001.jpg
    286.9 KB · Views: 1,048
  • Escanear0002.jpg
    Escanear0002.jpg
    119.5 KB · Views: 991

Apteryx

ACCESS: Confidential
Joined
Sep 28, 2007
Messages
152
Reaction score
20
Artie Bob:

Sorry, I didn't mean to imply that sheetmetal was ever cut on a prototype. Just that the logic of the wing plan escapes me.

Justo: thank you so much--I'd not seen those images! The planform of the version built in mockup is very p-39-like.

The 3-view I posted was declared to be a projected production version, with a cut-down rear fuselage and all-round vision canopy. And weird wings.

PS--Rereading my first post, I was being generally incoherent. I meant constant chord center section, not constant span.
 

red admiral

ACCESS: Top Secret
Joined
Sep 16, 2006
Messages
762
Reaction score
312
On a related note, does anyone have a picture of the Wright R-2160 Tornado engine?

Thanks
 

Apophenia

ACCESS: Top Secret
Senior Member
Joined
Jul 25, 2007
Messages
2,894
Reaction score
1,569
Four images of the preserved R-2160 Tornado at the Aviation Hall of Fame of New Jersey Museum (Teterboro, NJ).

http://www.fourfold.ca/billm/Aviation/AviationHallOfFameTeterboroNJ/AircraftEngines/pages/09WrightTornadoR2160.htm

Same collection: http://www.williammaloney.com/Aviation/AviationHallOfFameTeterboroNJ/AircraftEngines/index.htm
 

AeroFranz

ACCESS: Top Secret
Senior Member
Joined
May 4, 2008
Messages
2,394
Reaction score
429
Apteryx said:
My question: why do you think that a new design would feature a wing planform with a constant-span inboard section? There's no dihedral break; no constant width in the center to go with the constant span. You see what I'm saying here?

One could hypothesize that some overworked engineer just stuck that section in as an insert on the drawing to increase wing area to a specified amount, but one has a harder time believing the plane would have progressed to prototype status with that feature. But I may be missing something. Any thoughts?

there was another US aircraft of the period which was a collage of several different other fighters to facilitate manufacturing (was it a Boeing? the name 'Eagle' comes to mind for some reason*). Anyway, it used P-40 wings IIRC, and had inserts to achieve the design span. Maybe there is something like that going on here

*did some research. it's the Fisher Eagle. The P-40 outer panels were later replaced with P-51 panels.
 

Apteryx

ACCESS: Confidential
Joined
Sep 28, 2007
Messages
152
Reaction score
20
AeroFranz said:
there was another US aircraft of the period which was a collage of several different other fighters to facilitate manufacturing (was it a Boeing? the name 'Eagle' comes to mind for some reason*). Anyway, it used P-40 wings IIRC, and had inserts to achieve the design span. Maybe there is something like that going on here

There are several parallels between the P-69 and the Fisher P-75, but I think only the latter was a "Franken-fighter."

If the P-69 used somebody else's wings (and I can't tell whose those would be) they would have had to rework the whole main gear installation to have them where the drawing places them. Not a trivial undertaking!

It's just one of those mysteries--trivia, I suppose, but it will keep bugging me.
 

frank

ACCESS: Top Secret
Joined
May 20, 2006
Messages
617
Reaction score
22
The XP-75 used an SBD fuselage, tail & wing center section, P-40 wings & F4U landing gear. The XP-75A was an 'improved' redesign of that airframe. One proposal was to use P-51 wings, but that never happened. I think the landing gear location was the P-40's.



Apteryx said:
AeroFranz said:
there was another US aircraft of the period which was a collage of several different other fighters to facilitate manufacturing (was it a Boeing? the name 'Eagle' comes to mind for some reason*). Anyway, it used P-40 wings IIRC, and had inserts to achieve the design span. Maybe there is something like that going on here

There are several parallels between the P-69 and the Fisher P-75, but I think only the latter was a "Franken-fighter."

If the P-69 used somebody else's wings (and I can't tell whose those would be) they would have had to rework the whole main gear installation to have them where the drawing places them. Not a trivial undertaking!

It's just one of those mysteries--trivia, I suppose, but it will keep bugging me.
 

lark

ACCESS: Top Secret
Senior Member
Joined
Feb 17, 2006
Messages
1,811
Reaction score
122
For more about the Tornado engine and some drawings go to:

http://www.weakforcepress.com/tornado_2.htm
 

Steve Pace

Aviation History Writer
Joined
Jan 6, 2013
Messages
2,266
Reaction score
74
Does anyone have info and images re Republic XP-69.
 

Attachments

  • Republic XP-69.jpg
    Republic XP-69.jpg
    40.9 KB · Views: 902

XP67_Moonbat

ACCESS: Top Secret
Joined
Jan 16, 2008
Messages
2,174
Reaction score
131
How's this, Steve? ;)

http://www.weakforcepress.com/tornado_2.htm

http://home.att.net/~jbaugher1/p69.html

http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2270

http://www.anigrand.com/AA2069_XP-69.htm

Moonbat

PS- Just to give you a friendly heads-up, I think the mods might relocate this topic to EARLY PROJECTS.
 

Attachments

  • AA2069_XP-69_real_1.jpg
    AA2069_XP-69_real_1.jpg
    34.4 KB · Views: 145
  • AA2069_XP-69_real-3.jpg
    AA2069_XP-69_real-3.jpg
    27.3 KB · Views: 197
  • TACStudy.jpg
    TACStudy.jpg
    58.9 KB · Views: 192
  • TXP-69.jpg
    TXP-69.jpg
    131.1 KB · Views: 855

ysi_maniac

ACCESS: Confidential
Joined
Jan 26, 2007
Messages
81
Reaction score
10
You can even build a model :eek:
http://modelingmadness.com/scotts/allies/us/usaaf/xp69.htm
 

GeorgeA

ACCESS: Top Secret
Senior Member
Joined
Dec 31, 2006
Messages
705
Reaction score
77
Also, when a radial and a liquid-cooled engine do the same.

Definitely check out Kimble McCutcheon's book on the Wright R-2160 for (extensive) details.
 

Justo Miranda

ACCESS: Above Top Secret
Senior Member
Joined
Dec 2, 2007
Messages
5,351
Reaction score
4,723
Website
www.amazon.com
Some additional info-Post-1
 

Attachments

  • Escanear0001.jpg
    Escanear0001.jpg
    276 KB · Views: 377
  • Escanear0002.jpg
    Escanear0002.jpg
    590.3 KB · Views: 351
  • Escanear0003.jpg
    Escanear0003.jpg
    329.6 KB · Views: 316
  • Escanear0004.jpg
    Escanear0004.jpg
    256.7 KB · Views: 293

Justo Miranda

ACCESS: Above Top Secret
Senior Member
Joined
Dec 2, 2007
Messages
5,351
Reaction score
4,723
Website
www.amazon.com
Some additional info-Post-2
 

Attachments

  • Escanear0007.jpg
    Escanear0007.jpg
    227 KB · Views: 112
  • Escanear0006.jpg
    Escanear0006.jpg
    189.2 KB · Views: 104
  • Escanear0005.jpg
    Escanear0005.jpg
    308.1 KB · Views: 275

Justo Miranda

ACCESS: Above Top Secret
Senior Member
Joined
Dec 2, 2007
Messages
5,351
Reaction score
4,723
Website
www.amazon.com
Some additional info-Post-3
 

Attachments

  • Escanear0008.jpg
    Escanear0008.jpg
    128.8 KB · Views: 122
  • Escanear0009.jpg
    Escanear0009.jpg
    107.3 KB · Views: 320
  • Escanear0010.jpg
    Escanear0010.jpg
    236.6 KB · Views: 564

airman

ACCESS: Top Secret
Joined
Oct 14, 2007
Messages
1,301
Reaction score
153
Website
zeef.com
well, if i am not on mistake there was two proposed version of armament : or one cannon of 37 mm and two gun of 12,7 mm on each wing or classic three gun of 12,7 mm on each wing ! ::)
 

Kevin Renner

ACCESS: Confidential
Joined
Nov 6, 2007
Messages
101
Reaction score
9
Having seen pictures of Wrights 42 cylinder Tornado (offhand I can't recall if the engine is on display at Wright Patterson or not) along with skeleton cad drawings I have always wondered what the 70 cylinder version of the engine would of sounded like
 

frank

ACCESS: Top Secret
Joined
May 20, 2006
Messages
617
Reaction score
22
A radial doesn't 'have to be' air cooled.

GeorgeA said:
Also, when a radial and a liquid-cooled engine do the same.

Definitely check out Kimble McCutcheon's book on the Wright R-2160 for (extensive) details.
 

flateric

ACCESS: Above Top Secret
Staff member
Top Contributor
Senior Member
Joined
Apr 2, 2006
Messages
9,305
Reaction score
1,886
Justo - I just wonder how are you organazing million files named "EscanearXYZ.jpg" :)
 

GeorgeA

ACCESS: Top Secret
Senior Member
Joined
Dec 31, 2006
Messages
705
Reaction score
77
Yes, essentially Wright designed a 14-cylinder liquid-cooled radial and combined three units to make the 42-cylinder R-2160. A 70-cylinder (five 14-cyl) was contemplated, but in such long, multi-cylinder configurations, the weight of the crankshaft, the intake charge distribution, and cylinder head complexity become the limiting factors. Add in exhaust routing for the turbocharger and it gets really difficult.

Interestingly, Wright's later work on the stratified charge rotary included an eight-rotor design, with each rotor displacing 580 cubic inches.
 

Kevin Renner

ACCESS: Confidential
Joined
Nov 6, 2007
Messages
101
Reaction score
9
GeorgeA said:
Yes, essentially Wright designed a 14-cylinder liquid-cooled radial and combined three units to make the 42-cylinder R-2160. A 70-cylinder (five 14-cyl) was contemplated, but in such long, multi-cylinder configurations, the weight of the crankshaft, the intake charge distribution, and cylinder head complexity become the limiting factors. Add in exhaust routing for the turbocharger and it gets really difficult.

Interestingly, Wright's later work on the stratified charge rotary included an eight-rotor design, with each rotor displacing 580 cubic inches.

From the drawings I have seen the 14 cylinder two row sections each had their own crank shaft. The engine sections (think of the Tornado as a compound engine like the big Allison) would be connected together by lay shafts that ran in the Vee's between each bank of cylinders. Really I still don't think it as strange as the 18 cylinder engine in the Bugatti Veyron
 

Justo Miranda

ACCESS: Above Top Secret
Senior Member
Joined
Dec 2, 2007
Messages
5,351
Reaction score
4,723
Website
www.amazon.com
Please see Bugatti T67 V16 from http://www.secretprojects.co.uk/forum/index.php/topic,1100.45.html
 

Attachments

  • Escanear.jpg
    Escanear.jpg
    52.9 KB · Views: 143

Kevin Renner

ACCESS: Confidential
Joined
Nov 6, 2007
Messages
101
Reaction score
9
While the 16 cylinder Bugatti aircraft engine is a little on the different side I meant the one in the car that IMO is Ferdinand Piesch's (sp) wet dream
 

Stargazer2006

ACCESS: USAP
Senior Member
Joined
Jun 25, 2009
Messages
13,221
Reaction score
862

Attachments

  • xp69k.jpg
    xp69k.jpg
    33.7 KB · Views: 100
  • xp69j.jpg
    xp69j.jpg
    52.7 KB · Views: 97
  • xp69h.jpg
    xp69h.jpg
    39.1 KB · Views: 841
  • xp69g.jpg
    xp69g.jpg
    41.8 KB · Views: 881
  • xp69f.jpg
    xp69f.jpg
    34.1 KB · Views: 909
  • xp69e.jpg
    xp69e.jpg
    34.2 KB · Views: 930
  • xp69d.jpg
    xp69d.jpg
    59.3 KB · Views: 984
  • xp69l.jpg
    xp69l.jpg
    32.7 KB · Views: 107

Apteryx

ACCESS: Confidential
Joined
Sep 28, 2007
Messages
152
Reaction score
20
CAO 700 said:
The Anigrand kit looks really great!
Yes, I covet the kit. The nagging question I have about this version of the XP-69, and yes, I've raised it before, is: what is with the constant-chord center section on the wing? It appears in some drawings of the plane, but not anything I've seen that's contemporary with its development. And what sense does it make? It's constant-chord but not constant thickness. Nor is there a dihedral break, with a horizontal center-section, as in the T-6 Texan or the XP-75.

I just got a copy of Tornado: Wright Aero's Last Liquid-cooled Piston Engine. It's a wonderful reference, and I hope the author can fulfill his stated intention of writing a series of books on experimental engines. It has this nugget re the XP-69:
"One interesting finding of the full-scale tunnel testing...was that the aileron forces were too high. Several solutions were proposed, including an internal sealed balance with wedge trailing edge."

I never heard of a "wedge trailing edge" but maybe that's the origin of the kink in the trailing edge? Doesn't explain the kinked leading edge, though.
 

Stargazer2006

ACCESS: USAP
Senior Member
Joined
Jun 25, 2009
Messages
13,221
Reaction score
862
No less than 57 pictures on NASA's CRgis website from the 3/4 scale model wind tunnel tests:

http://crgis.ndc.nasa.gov/historic/Test_139:_XP-69_3/4%E2%80%93scale_Model_%28Stability_and_Cooling%29

800px-LMAL_29688.JPG
 

kmccut

ACCESS: Restricted
Joined
Aug 5, 2011
Messages
16
Reaction score
2
Website
www.weakforcepress.com
Apteryx said:
Republic Aircraft had a WWII fighter project to be powered by a single Wright Tornado engine mid-mounted, a la the Airacobra. It was a new project, and not a development of their P-47.

In 2001 I published a book on the Wright Tornado aircraft engine that included a section on the Republic XP-69, one of the aircraft that was intended to use the engine. Please see
http://www.weakforcepress.com/

At that time my book contained the most complete information that had been published on the XP-69. In 2001 available sources all agreed that the XP-69 was a mid-engine fighter with the propeller driven via an extension shaft.

I have since discovered a drawing of the XP-69 at the U.S. National Archives that clearly shows a conventional tractor engine installation. This is the only drawing of Republic design AP-18 that I have ever seen. Please see
http://www.weakforcepress.com/XP-69/index.html and
http://www.weakforcepress.com/tornado_errata.htm


I apologize for the poor quality; the drawing was too large to duplicate with any of the equipment available at NARA, so I was forced to hang drawing and photograph it in sections.

The drawings clearly show the engine in front of the pilot and the space behind the pilot filled with the ducts, radiators, intercoolers, etc. required for a liquid-cooled turbosupercharged engine installation.

The unfortunate thing is that I discovered this drawing AFTER I had published my book on the Wright Tornado. In retrospect, I DID have details of the ducting and heat exchangers behind the pilot and should have realized while writing the book that there was no room for the engine behind the pilot.

The Republic AP-18 design is thought to be an evolution of the AP-12 design, which DID have a mid-mounted engine. It appears historians may have incorrectly assumed the AP-18 was a mid-engine aircraft also.
 

Stargazer2006

ACCESS: USAP
Senior Member
Joined
Jun 25, 2009
Messages
13,221
Reaction score
862
Very interesting, Kimble.

Thank you very much for sharing. The XP-69 is a pet might-have-been aircraft of mine, and these documents shed valuable new light on the subject.

Any idea if Republic ever planned a popular name for it (like Thunder-something)?
 

Similar threads

Top